CEDAR RAPIDS — A report showing no relationship between atrazine and cancer is not the final word on the weed killer’s safety, says a University of Iowa researcher.

The report was issued as part of the Agricultural Health Study, a long-term research project that has been tracking the health of nearly 90,000 people — certified pesticide applicators and their spouses — in Iowa and North Carolina since 1994.

Tim Pastoor, principal scientist with Syngenta Corp., the primary maker of atrazine, was in Iowa this week, touting a report issued from the study in late May.

Tim Pastoor

“I am happy to say, they found absolutely no relationship between atrazine usage and any form of cancer,” Pastoor said Monday, June 27, during a meeting with The Gazette Editorial Board. “This is, certainly in our view, good news.”

The report is especially significant in Iowa, where atrazine is the second most commonly used herbicide in the state’s cornfields, behind Roundup. It is also sprayed on golf courses, lawns and roadsides.

“I can’t say (a link) is never going to show up,” said Dr. Charles Lynch, a UI epidemiology professor and director of the Iowa portion of the Agricultural Health Study. “The vast majority of cancers have yet to develop in this cohort.”

Lynch noted that the average age of study participants is 60 and more than 90 percent are still alive.

Dr. Charles Lynch

“There are still many years of living left to do in this cohort,” he said. “As more cases of disease develop, these need to be investigated further.”

Nationwide, 60 million to 80 million pounds of atrazine is applied to corn, sorghum and sugar cane every year.

Environmentalists have questioned the chemical’s effects on wildlife, particularly frogs and other amphibians, and claim the herbicide is linked to birth defects and other health problems, including cancer.

The European Union banned atrazine in 2004 because of water contamination.

Pastoor said despite more than 6,000 studies in the 51-year history of atrazine that prove its safety, the Environmental Protection Agency is reviewing its registration decision on the herbicide.

Some of those studies have been funded by Syngenta, he said, but the Agricultural Health Study is an independent project sponsored by the Environmental Protection Agency and the National Institutes of Health.

“Atrazine is easily, in my opinion, one of the best studied pesticides ever,” Pastoor said, noting the chemical is in 59 products. “They make these products work better, so age has its benefits.”

Results from the study showed that of 36,357 applicators who reported using atrazine, 3,146 were diagnosed with cancer.

“Overall, there was no consistent evidence of an association between atrazine use and any cancer site,” the report concluded. “There was a suggestion of increased risk of thyroid cancer, but these results are based on relatively small numbers and minimal supporting evidence.”

Lynch said the report is one of many issued from the study; more will be issued in the future.

The goal is to follow participants until death.

“We’ll see more outcomes — cancers and deaths — in the years ahead,” Lynch said.

One surprising conclusion so far is that farmers have lower mortality rates than the general population, generally 60 percent of the rate of others the same age in Iowa and North Carolina.

Lynch said participants’ healthier lifestyles, with greater on-the-job physical activity and lower cigarette use, may contribute to lower rates of the nation’s leading killers, heart disease and cancer.